Iain Duncan Smith's department has made a formal complaint to the BBC claiming its coverage of the government is biased.

The work and pensions secretary singled out the broadcaster's economics editor, Stephanie Flanders, for the harshest criticism, accusing her of "peeing all over British industry".

Officials at the BBC defended its record of impartiality and Flanders' reporting. But Duncan Smith told a Sunday newspaper that the BBC diminishes the role of the government in good news but "dumps" on it when the story is bad.

His department has formally complained to the BBC head of news, Helen Boaden, about the broadcaster's "carping and moaning".

The minister appeared particularly angered by coverage this week of the unexpected drop in the unemployment rate to 8%. The jobless total fell by 46,000 in the quarter to June to 2.56 million, with the number of people claiming jobseeker's allowance last month at 1.59 million, down by 5,900 on June.

He told the Mail on Sunday: "The BBC is locked to the reading of the economy that is run out of Ed Miliband and Ed Balls' office. They think if only you spend and borrow more money you can create growth everywhere.

"This is the general tenor of everything that comes out of the BBC. They expected the [employment] figures to be flatlining.

"They convinced themselves youth unemployment would continue to rise, but when it fell they were in a complete quandary.

"Stephanie Flanders poured cold water over the whole thing. She said: 'Of course this is good news, but it could be because we aren't productive enough.'"

Flanders also wrote in her BBC blog last week about the apparent contradiction between 201,000 more people finding work in the previous three months while output fell 0.7%. Among the possible answers explored by the award-winning journalist were that the Office for National Statistics has been underestimating growth, that a rise in part-time and self-employed workers who would like to work more hours is flattering the jobs figures, and that companies are "hoarding" good staff while they wait for good times to return.

"Why not just sit back, and enjoy the novelty?" added Flanders. "The trouble is that the longer the puzzle continues, the more potentially worrying it becomes, because it becomes less and less likely that simple measurement error explains it."

Duncan Smith added: "If the unemployment figures had gone up, we would have been on the BBC TV News at Six and Ten and would have got the blame."

He added: "When the news is good, the BBC view is: 'Get the government out of the picture quickly, don't allow them to say anything about it.'

"When the news is bad, [it's]: 'Let's all dump on the government.'

"Last month, there was a marginal rise in youth unemployment so they centred on that.

"This time it came down so they cast doubt on the figures. [Flanders] said it could be industry is so bad they have to take on two people where one person could do the job.

"She was peeing all over British industry and the private sector. It was terrible. Our private industry is unbelievably robust compared to much of Europe."

Commenting on Duncan Smith's interview, Liam Byrne, the shadow work and pensions secretary, said: "The work and pensions secretary should stop moaning about how this mess is being reported and start doing something about it."

The BBC said: "BBC News is confident our coverage of this story was impartial, fair and balanced, reflecting a wide range of views. Indeed Mr Duncan Smith expressed his position on several BBC outlets.

"Stephanie interrogated numerous aspects of the figures in her analysis. She echoed questions raised by many experts, including the deputy governor of the Bank of England as well as noting the rise in the number of people in work was good news."

The DWP said: "The department made a complaint regarding the coverage of the employment figures on the Six O'Clock News and News at 10. The secretary of state has made his views clear in the Mail on Sunday."